Beam splitter and method for generating equal optical path length beams

Abstract

The present invention is a beam splitter for splitting an incident beam into first and second beams so that the first and second beams have a fixed separation and are parallel upon exiting. The beam splitter includes a first prism, a second prism, and a film located between the prisms. The first prism is defined by a first thickness and a first perimeter which has a first major base. The second prism is defined by a second thickness and a second perimeter which has a second major base. The film is located between the first major base and the second major base for splitting the incident beam into the first and second beams. The first and second perimeters are right angle trapezoidal shaped. The beam splitter is configured for generating equal optical path length beams.

What is claimed is:  
     
       1. A beam splitter for splitting an incident beam into first and second beams, said beam splitter comprising: 
       a first prism defined by a first thickness and a first perimeter, said first perimeter having a first major base;  
       a second prism defined by a second thickness and a second perimeter, said second perimeter having a second major base; and  
       a film located between said first major base and said second major base for splitting the incident beam into the first and second beams,  
       wherein said first and second prisms are configured so that the first and second beams have a equal optical path length, fixed lateral separation and are parallel upon exiting.  
     
     
       2. A beam splitter as defined in  claim 1  further comprising 
       a distance M is defined as the beam path distance from said second major base to said second minor base;  
       a distance B defined as the fixed lateral separation;  
       a distance A defined as the beam path distance from said first major base to proximal said first minor base whereby 2M=2A+B.  
     
     
       3. A beam splitter as defined in  claim 1  wherein 
       said first beam's optical path length is equal to 2A+B;  
       said second beam's optical path length is equal to 2M whereby 2M=2A+B.  
     
     
       4. A beam splitter as defined in  claim 1  wherein: 
       said first perimeter is trapezoidal shaped and further comprises a first minor base, a first reflecting side, and a first nonreflecting side, said first reflecting side forming a right angle with said first major base; and  
       said second perimeter is trapezoidal shaped and further comprises a second minor base, a second reflecting side, and a second nonreflecting side, said second reflecting side forming a right angle with said second major base.  
     
     
       5. A beam splitter as defined in  claim 4 , wherein said first nonreflecting side intersects said first major base at a 45 degree angle and said second nonreflecting side intersects said second major base at a 45 degree angle. 
     
     
       6. A beam splitter as defined in  claim 5 , wherein said first nonreflecting side and said second nonreflecting side are arranged to intersect at a right angle. 
     
     
       7. A beam splitter as defined in  claim 6 , wherein said first major base is shorter than said second major base. 
     
     
       8. A beam splitter as defined in  claim 1 , wherein said film has a substantial ratio of 1:1 between transmissivity and reflectivity. 
     
     
       9. A beam splitter as defined in  claim 1 , wherein said an incident beam is directed perpendicularly at said first nonreflecting side of said beam splitter so that said incident beam splits into first and second beams at said film, said first beam reflecting within said first prism, passing through said film and to exit through said second nonreflecting side, said second beam reflecting within said second prism, reflecting off said film to exit through said second nonreflecting side, said first and second beams having a fixed lateral separation, and being parallel upon exiting. 
     
     
       10. A method of generating equal optical path length beams, said method comprising the steps of: 
       providing a beam splitter having:  
       a first prism defined by a first thickness and a first perimeter, said first perimeter being trapezoidal shaped having a first major base, a first minor base, a first reflecting side, and a first nonreflecting side, said first reflecting side forming a right angle with said first major base;  
       a second prism defined by a second thickness and a second perimeter, said second perimeter being trapezoidal shaped having a second major base, a second minor base, a second reflecting side, and a second nonreflecting side, said second reflecting side forming a right angle with said second major base; and  
       a film located between said first major base and said second major base, said film having substantially ratio of 1:1 between transmissivity and reflectivity; and  
       directing an incident beam perpendicularly at said first nonreflecting side where said incident beam splits into a first and a second beams at said film, said first beam reflecting within said first prism, passing through said film and to exit through said second nonreflecting side, said second beam reflecting within said second prism, reflecting off said film to exit through said second nonreflecting side, said first and second beams having a fixed lateral separation, and being parallel upon exiting.  
     
     
       11. A method as defined in  claim 10 , further comprising configuring said first and second prisms whereby said first and second beams have an equal optical path length upon exiting. 
     
     
       12. A method as defined in  claim 10 , further comprising configuring said beam splitter having a distance M defined as the beam path distance from said second major base to said second minor base; having a distance B defined as the fixed lateral separation; and having a distance A defined as the beam path distance from said first major base to proximal said first minor base whereby 2M=2A+B. 
     
     
       13. A method as defined in  claim 10 , wherein said first beam's optical path length is equal to 2A+B; said second beam's optical path length is equal to 2M; whereby 2M=2A+B. 
     
     
       14. A method as defined in  claim 10 , wherein said second beam is perpendicular to said nonreflecting side of said second trapezoid. 
     
     
       15. A method as defined in  claim 10 , wherein said first beam is said perpendicular to said nonreflecting side of said second trapezoid.